Multi-axially controllable manipulators are known and are generally described as robots in industrial applications. The free end of the robot, which can be equipped with, for example, a spraying head or welding head, travels along a more or less complex movement path, in which predetermined operations are performed in certain positions or while travelling along certain paths. The path to be travelled and the operations to be performed are fixed in a program, which is read out by the control means and converted into control signals for commanding actuators. Writing such a program is generally a complicated and time-consuming job and is therefore undertaken only in the case of repetitive movement patterns, as in the case of processing mass-produced products.
The programming work can be reduced by using so-called teach-in programming, in which the free end of the robot or manipulator travels along the desired movement path under manual control, which movement path is simultaneously recorded in a program, and which program can then be entered in the control means for commanding the actuators.
A multi-axially controllable manipulator of the above-described type for use in the case of non-repetitive movement patterns is known from U.S. Pat. No. 3,637,092. This known control system is generally described as a master-slave system, in which the slave--the manipulator--accurately follows the movements of the master--the miniature model of the manipulator--with little or no time delay.
The operator of the system has to maintain a close watch on the end of the manipulator in this case, in order to avoid collisions thereof with the object to be handled, for example a load to be gripped and then lifted.
In the case of a manipulator in the form of an X-ray apparatus, the free end of which is equipped with a C-shaped supporting arm which is provided at one end with an X-ray source and at the opposite end with an image sensor, the problem occurs that, although on the face of the X-ray apparatus can be moved into approximately the desired position relative to a patient to be examined with it, the correct, accurate relative position of X-ray apparatus and patient must be determined with the aid of the image which the image sensor displays on a screen set up for the operator, in this case the radiologist. The image displayed on the screen gives no information on the precise relative distance between the X-ray source and the patient to be examined, so that there is a risk that when the X-ray source is displaced "by feel", with the operator's eye directed at the screen, a "collision" between X-ray source and patient can occur, with the chance of serious injury for the patient.
The object of the invention is to provide a control system for a manipulator of the above-described type, which permits a rapid displacement of the free end thereof along a continuous movement path, in which collisions between the manipulator and the object to be examined or handled are ruled out with absolute certainty.
This object is achieved according to the invention through the fact that the control means comprise a miniature model of the object to be treated with the manipulator, while the scale ratio of the miniature model of the object to be treated is greater than the scale ratio of the miniature model of the manipulator, in order to form a collision-free safety zone in the immediate surroundings of the object to be treated.
By moving the miniature model of the manipulator by hand relative to the miniature model of the object to be treated, which is also made substantially to scale, while the movements--generally angular displacements--of the parts of the scale model are relayed in the ratio 1:1 to actuators of the manipulator by means of control signals generated by the position transducers, the free end of the manipulator can be moved into the correct position relative to the object to be examined, and the operator's attention need not be divided between the screen, on the one hand, and the actual movement of the free end of the manipulator, on the other. The movement of the manipulator can be controlled simultaneously over more than two axes.
Due to the fact that the miniature model of the object has a greater scale ratio than the scale ratio of the miniature model of the manipulator, collisions between a manipulator bearing an X-ray system and the patient to be examined therewith are avoided with absolute certainty.
If for example, 1:10 is selected as the scale ratio of the miniature model of the manipulator, and the miniature model of the object to be examined is 1:9, the operator can shift the free end of the manipulator scale model over a surface of the object miniature model, while the manipulator in this case remains at a distance from the object to be examined. With a safety zone thus created, the operator, in this case the radiologist, can shift the miniature model of the manipulator "by feel" and keep his/her attention fixed on the X-ray image, displayed on a screen, of the part of the patient's body to be examined.
According to an alternative embodiment of the invention, the object can also be achieved through the fact that the control means also comprise a miniature model of the object to be treated with the manipulator, the scale ratio of the miniature model of the manipulator being locally greater than that of the miniature model of the object through the local application of a material layer in order to form a safety zone.
Such a measure can be achieved by, for example, applying a layer of material of a certain thickness to the part of the miniature model of the manipulator corresponding to the X-ray source. The safety zone thus created also has the advantage that different objects of slightly different sizes can be examined with the same object miniature model.
It can be desirable for the manipulator to be brought into contact at several discrete points with the object to be examined or to be treated. At those points a "hole" must therefore be present in the safety zone. Such a "hole" is preferably obtained by making the object miniature model locally in a different scale ratio from the remainder of said miniature model, for example giving it a scale ratio which is the same as or smaller than that of the manipulator miniature model.
In the case of an object miniature model with scale ratio 1:9 and a manipulator miniature model with scale ratio 1:10, the object miniature model is also made at a certain point with a scale ratio 1:10, with the result that contact between manipulator and object is possible only at that point.
It may be desirable for the object to be examined or treated to be movably supported on a vertically adjustable and/or tiltable table which can be moved in the longitudinal direction.
This is, for example, the case during the X-ray examination of patients. In that case the miniature model of the object must rest on a miniature model of the supporting table, which is movable in the same way as the actual supporting table, and which is connected thereto in such a way that the miniature model and the supporting table always assume identical positions .